It’s possible that I shall make an ass of myself. But in that case one can always get out of it with a little dialectic. I have, of course, so worded my proposition as to be right either way (K.Marx, Letter to F.Engels on the Indian Mutiny)
SANTA CRUZ, Calif. – Dark matter is one of the oldest open problems in physics. It makes up most of the matter in the universe and shapes how galaxies form and move, yet no one has ever directly detected it. Physicists have proposed dozens of candidates to explain it: exotic new particles, black holes formed moments after the Big Bang, and more.
Returning to ‘naturalness’
With no direct detection to settle the question, researchers often fall back on a different test: not “is this candidate detected,” but “is this candidate natural.” Naturalness is physics’ version of Occam’s razor. A theory is called natural if it explains the universe we see without requiring its underlying numbers to be delicately, almost implausibly, fine-tuned. A theory that only works if several unrelated quantities happen to cancel out to many decimal places is treated with suspicion, even if it isn’t strictly ruled out.
Naturalness has quietly guided decades of research into which ideas are worth pursuing, but it’s a slippery concept: intuitive to invoke, hard to pin down, and rarely applied evenhandedly across competing ideas.
That’s the gap Stefano Profumo, professor of physics at the University of California, Santa Cruz, addresses in a new paper published in Physical Review D. Rather than debating naturalness in the abstract, Profumo puts it to a direct, quantitative test, applying the same yardstick to two very different dark matter candidates: subatomic particles, and primordial black holes—the latter being hypothetical phenomena forged in the first fraction of a second after the Big Bang, long before stars existed to collapse into them.
Measuring fine-tuning across models
That yardstick, called the Barbieri-Giudice measure, asks a simple question of any model: If you nudge one of its input numbers by a tiny amount, how much does the predicted outcome swing? A gentle swing means the model is forgiving of its own assumptions, and hence, natural. A wild swing means the model only works because its numbers have been tuned within a hair’s breadth of what’s required.
Profumo ran 12 well-studied dark matter scenarios through this test, including several flavors of particle dark matter—like the long-favored “WIMP,” or weakly interacting massive particle—and several distinct ways primordial black holes could have formed in the early universe. The result cuts against a common assumption in the field.
Dark matter candidates are often labeled “natural” or “fine-tuned” as entire categories, but this comparison tells a more nuanced story. Each bar shows how sensitively the predicted amount of dark matter responds to small changes in a model’s underlying parameters; longer bars indicate that more precise adjustment is required. Particle candidates and primordial-black-hole scenarios appear across the spectrum, showing that fine-tuning depends primarily on how dark matter is produced—not simply on what dark matter is (graphic created with OpenAI Codex, based on Fig. 6 in Profumo’s new paper).
“There’s a habit of treating primordial black holes as the exotic, fine-tuned alternative, and particle dark matter as the safe, natural default,” said Profumo, deputy director for theory at the Santa Cruz Institute for Particle Physics. “When you actually run the numbers side by side, that story doesn’t hold up. Some black hole scenarios are about as natural as it gets. Some particle scenarios are wildly fine-tuned. And some of each land right in the middle.”
For instance, black holes formed from collapsing networks of structures called “domain walls” came out among the most natural constructions in the entire study, rivaling the most forgiving particle models. Meanwhile, one of the most popular particle scenarios, in which dark matter annihilates through a resonance tied to the Higgs boson, turned out to be among the most fine-tuned scenarios Profumo examined, requiring one of its numbers to be pinned down to within a fraction of a percent. Other constructions, on both sides, fell somewhere in between.
Challenging common assumptions
“Naturalness has real power as a filter for deciding where to look next,” Profumo said. “But it can’t be a shortcut for dismissing an entire category of ideas, like primordial black holes, just because a few individual models within that category happen to be tuned. The tuning lives in the specific model, not in the kind of dark matter you started with.”
The paper doesn’t identify a winner. Instead, it offers researchers a common ruler for comparing vastly different dark matter proposals on equal footing—and a caution against letting a single word like “natural” do more work than it’s earned.
Physicists at the University of Oxford have helped confirm that one of the strangest phenomena in physics - quantum entanglement - occurs even among some of the heaviest and most fleeting particles ever created. The discovery, made using the world’s most powerful particle collider at CERN, has been published in Physical Review Letters.
Entanglement is the phenomenon in which two particles from the same origin remain connected, even if they move far apart in time and space. If something affects one particle, it will also affect all the particles with which it is entangled. This means that measuring a property of one particle instantly tells you something about its entangled partner/s, no matter how distant they are.
Albert Einstein famously called entanglement ‘spooky action at a distance,’ and the phenomenon has been demonstrated in a range of systems, including photons, electrons and trapped ions. Today, entanglement is no longer just a curiosity: it underpins emerging technologies such as quantum computers, ultra-secure quantum communication networks and next-generation sensors. For instance, in quantum computing, entanglement is used to manipulate multiple qubits in a single operation, rather than individually. This allows multiple calculations to be performed simultaneously.
However, it was unknown whether quantum entanglement remains intact under more extreme conditions – such as the short-lived particles produced during highly energetic collisions. To test this, an international collaboration used the ATLAS experiment at CERN’s Large Hadron Collider (LHC) near Geneva, Switzerland. The team looked for entanglement in an entirely new setting: pairs of Z bosons that exist for only a fraction of a second before decaying.
The Z bosons studied were produced in the decay of a Higgs boson - the particle discovered at the LHC in 2012 - which briefly splits into two Z bosons before each one decays further into pairs of electrons or muons. The Higgs bosons are generated by smashing together protons travelling at 99.99% the speed of light: collisions that have energies of thirteen trillion electron volts.
Although the Z bosons vanish almost instantly, the ATLAS detector can precisely track the electrons and muons they leave behind. By reconstructing the angles at which these particles were emitted, the researchers could infer the spins of the original Z bosons and test whether they were linked by quantum entanglement. The results showed strong evidence that they were. This makes it one of the highest-energy confirmations of quantum entanglement ever recorded.
Professor Barr said: ‘We’re used to thinking of entanglement as something delicate, seen in laboratory experiments with single photons. Finding it alive and well among particles as heavy and short-lived as Z bosons, created in some of the most violent collisions we can produce on Earth, shows just how fundamental and robust this quantum effect really is. It’s a nice reminder that the same strange rules of quantum mechanics that may one day power quantum computers are at work everywhere in nature, even at the extreme energies of the Large Hadron Collider.’
Beyond its fundamental significance, the research adds to a growing effort by physicists to borrow tools and ideas from quantum information science (the field behind quantum computing) and apply them to particle physics. This cross-pollination is helping scientists develop new, more sensitive ways of analysing collider data, with the potential to reveal subtle effects that might point to physics beyond our current understanding of the universe.
At Oxford University, Professor Barr co-leads a major interdisciplinary project exploring the foundations of quantum mechanics at high energies. Besides empirically testing quantum effects at the smallest possible scales and highest energies, the project is also investigating the philosophical implications of these measurements and what they may tell us about the fundamental nature of reality.
Project co-PI Professor Chris Timpson (Faculty of Philosophy) said: ‘Entanglement is both the most promising and the most puzzling aspect of quantum reality; these collider experiments detecting entanglement present a new frontier in investigations of the foundations of quantum mechanics.’
Oxford University researchers are also involved in the upgrade currently taking place on the ATLAS detector. Combined with the upgraded High-Luminosity Large Hadron Collider, this will allow researchers to undertake even more profound explorations of quantum phenomena and apply novel quantum information techniques to exploit the huge data sets that this machine will deliver.
Professor Daniela Bortoletto (Department of Physics, University of Oxford), who is the UK coordinator for producing the modules for the upgraded ATLAS detector’s pixel system, said: ‘This measurement demonstrates the scientific power of the ATLAS collaboration and the unique capabilities of CERN's Large Hadron Collider. Oxford researchers have played a leading role in developing these new approaches to studying quantum phenomena at the highest energies, and we are proud to contribute to an international effort that is opening new ways to explore the fundamental laws of nature.’
The study ‘Measurements of Z-boson pair entanglement in decays of Higgs bosons at the ATLAS experiment’ has been published in Physical Review Letters.
Oxford University has been placed number 1 in the Times Higher Education World University Rankings for the tenth year running, and number 3 in the QS World Rankings 2024. At the heart of this success are the twin-pillars of our ground-breaking research and innovation and our distinctive educational offer.
Oxford is world-famous for research and teaching excellence and home to some of the most talented people from across the globe. Our work helps the lives of millions, solving real-world problems through a huge network of partnerships and collaborations. The breadth and interdisciplinary nature of our research alongside our personalised approach to teaching sparks imaginative and inventive insights and solutions.
Through its research commercialisation arm, Oxford University Innovation, Oxford is the highest university patent filer in the UK and is ranked first in the UK for university spinouts, having created more than 300 new companies since 1988. Over a third of these companies have been created in the past five years. The university is a catalyst for prosperity in Oxfordshire and the United Kingdom, contributing around £16.9 billion to the UK economy in 2021/22, and supports more than 90,400 full time jobs.
The Northern Lights, which occur when particles from the Sun enter the Earth’s atmosphere, generate brilliant sky displays in our Northern Hemisphere, offering an occasional cosmic show enjoyed by millions.
But how collisions between these particles, or low-energy cosmic rays, and the Earth’s gases result in the Northern Lights are less well-understood.
Even more puzzling are collisions involving high-energy cosmic rays, which possess more than one million times the energy than those from the Sun and emanate from exploding stars, or supernovae. Scientists have typically relied on computer simulations to unpack their collision with Earth’s atmosphere, but these methods have produced varied, and sometimes conflicting, results.
New research by an international team of physicists takes an unprecedented approach that offers a clearer understanding of these interstellar wonders.
Using CERN’s Large Hadron Collider, the scientists have recreated how high-energy cosmic rays enter the Earth’s atmosphere and collide with our planet’s gases.
The results, reported in the journal Physical Review Letters, help decipher the origins of interstellar particles from the cosmos.
“We now have a better understanding of how particles from objects more exotic than the Sun interact with our atmosphere,” says Jesse Liu, a New York University assistant professor of physics who led the research. “By advancing our knowledge of high-energy cosmic collisions in the Earth’s atmosphere, we have taken another step to unraveling the many mysteries of our universe.”
“The published results are indeed something special because these data are unique, and in our measurements, we were able to show that our previous models for this type of interaction are actually very inaccurate,” adds Cigdem Issever, a physicist at Humboldt-University of Berlin and one of the paper’s authors.
Recognizing the limitations of computer simulations, Liu, Issever, and their colleagues, who included scientists from Hamburg’s DESY Research Center, turned to the Large Hadron Collider (LHC)—the world’s most powerful particle physics machine, located outside of Geneva—to devise an innovative experiment that mimics how high-energy cosmic rays collide with the Earth’s atmosphere.
Focusing on oxygen’s foundational role in Earth’s atmosphere, the scientists introduced oxygen beams for the first time in the LHC and collided them with LHC-generated proton beams, which replicate the cosmic rays that emanate from supernovae. The results constituted the world’s first measurements of cosmic rainstorms recreated in controlled-lab conditions.
The researchers took millions of closeup photos of these outcomes using a 100-million-pixel camera that captures the aftermath of proton collisions that occur up to 40 million times per second.
Part of CERN’s ATLAS collaboration, which is exploring the fundamental nature of matter and the basic forces that shape the universe, the sophisticated device measured the number, energies, and angles of particles made in the proton-oxygen collision to offer precise portraits of the birth of these cosmic rainstorms.
“These new results significantly sharpen our knowledge of these subatomic interactions and will help us further explore the nature of cosmic particles raining from the sky,” concludes Liu.
Measurement of Charged-Particle Production in √𝑠NN =9.62 TeV Proton-Oxygen Collisions as a Probe of Cosmic-Ray Air Showers with the ATLAS Detector
Article Publication Date
14-Sep-2026
Friday, August 07, 2026
Research data infrastructure: getting more insights from every experiment
National research data infrastructure funded with EUR 71 million – KIT participates in five consortia dedicated to environmental, materials, and fundamental physics research
The KATRIN neutrino experiment conducted at KIT generates large quantities of data. The NFDI ensures that this data remains available for future research questions in other disciplines as well. (Photo: Markus Breig, KIT)
The five consortia where KIT is involved cover a broad range of research topics including environment and climate, materials sciences, and physics fundamental research.
Climate change, extreme weather events, and natural hazards present growing challenges for policymakers, public authorities, and municipalities. Planning flood protection, securing water resources, or developing measures for the adaptation to climate change – all this requires large amounts of environmental and climate data. However, this data is often stored in different formats and systems, making it difficult to evaluate them together. The NFDI4Earth consortium facilitates access to this data: “Through a centralized portal, researchers have quick and easy access to data on climate, the environment, and natural hazards,” said Professor Jan Cermak, head of KIT’s Institute of Meteorology and Climate Research Atmospheric Trace Gases and Remote Sensing. “Our aim now is to refine these offers together with the scientific community and to make sure that any knowledge gained will be incorporated more quickly, for example, into climate adaptation and risk prevention measures.”
Making Better Use of the Potential of Expensive Large-scale Research Facilities
Research facilities investigating photons and neutrons generate measurement data of high scientific value. In many cases, such data can only be reused to a limited extent later on, while its collection usually requires considerable investments from the public sector. The DAPHNE4NFDI consortium ensures that such datasets are preserved for the long term so that they are available for new scientific research questions. “This significantly increases the return on public investments for new and complex research infrastructures, as the data is not only used for the project in which it is generated, but far beyond. Thus, it forms the basis of other scientific and technological developments,” said Professor Jan-Dierk Grunwaldt from KIT’s Institute for Chemical Technology and Polymer Chemistry. In the second funding phase, digital and AI-based tools are expected to help make research faster and more reproducible.
Developing New Materials Faster
Be it more powerful batteries, more resilient materials, or more sustainable production methods: Developing new materials requires the collaboration of many research groups and the exchange of huge amounts of data. This was complicated in the past due to differing data formats and missing standards.
To address this problem, the NFDI-MatWerk consortium is going to establish common standards and develop digital tools for materials research. This enables the researchers to exchange data on the structure, properties, and production of materials, evaluate it together, and design new materials in a more targeted manner. “Today, developing and handling advanced materials is hardly conceivable without exchanging large quantities of data,” said Professor Peter Gumbsch from KIT’s Institute for Applied Materials.
FAIRmat also aims to advance materials research through a powerful data infrastructure. This was the motivation for building the international NOMAD platform, which is meanwhile being used by thousands of researchers. “If you want to develop new materials, it must be possible to efficiently evaluate results from experiments and simulations and compare them to each other,” said Professor Christof Wöll from KIT’s Institute of Functional Interfaces. “Our NOMAD platform supports scientists in documenting data systematically, automating workflows, and sharing research results. This creates the basis for reproducible, data-driven, and increasingly AI-based materials research.”
Exploring the Origin of the Universe
How did the universe come into being? What is matter made of? And what are the forces that hold the world together at its core? Researchers are conducting some of the most extensive experiments worldwide to find answers to these questions. Here, large amounts of data are generated, which need to be preserved for the long term, processed, and made usable across various research disciplines. The PUNCH4NFDI consortium makes a contribution to this end by developing common data and computing infrastructures. Research in this sector has yielded fundamental insights in recent years, including the discovery of the Higgs boson, the detection of the quark gluon plasma, and the first image of the black hole at the center of the Milky Way.
“KIT pools two key strengths in the consortium: our expertise in managing large, distributed research data repositories and our leading role in astroparticle physics,” said Dr. Andreas Haungs from KIT’s Institute for Astroparticle Physics. “Especially in multi-messenger astrophysics, which combines data from telescopes, gravitational wave and particle detectors, information from different experiments must be available in near real-time so that it can be analyzed cooperatively by the researchers. We’ll continue to further refine our high-performance infrastructures.”
Long-Term Future of NFDI Secured
Along with the current funding decision, the German federal and state governments have decided to continue funding the National Research Data Infrastructure in the long term and to further develop its structure. This secures the existence of the services set up over the past years and establishes them as the central infrastructure of the German research landscape.
In close partnership with society, KIT develops solutions for urgent challenges – from climate change, energy transition and sustainable use of natural resources to artificial intelligence, sovereignty and an aging population. As The University in the Helmholtz Association, KIT unites scientific excellence from insight to application-driven research under one roof – and is thus in a unique position to drive this transformation. As a University of Excellence, KIT offers its more than 10,000 employees and 22,800 students outstanding opportunities to shape a sustainable and resilient future. KIT – Science for Impact.
Friday, July 03, 2026
World’s largest particle smasher halts for upgrade to boost hunt for dark matter
Some of the 1232 dipole magnets that bend the path of accelerated protons are pictured in the Large Hadron Collider (LHC), which will be shut down for four years of renovations – Copyright AFP/File VALENTIN FLAURAUD
The world’s most powerful particle accelerator will shutter operations on Monday for four years of renovations to dramatically boost its collision-capacity and the potential for unlocking one of the greatest mysteries of the Universe: dark matter.
The Large Hadron Collider (LHC) is a 27-kilometre proton-smashing circular tunnel at the heart of Europe’s physics lab CERN near Geneva. It has most famously been used to prove the existence of the Higgs boson, dubbed “the God particle.”
In the tunnel, running about 100 metres below the French-Swiss border area, superconducting magnets and accelerating structures propel particles to extreme energies and then smash them together at phenomenal speeds.
But from Monday, activity will stop, as the extraordinary device undergoes upgrades aimed to further increase the precision and intensity of particle collisions.
Once completed, the enhanced particle smasher, donning the enhanced name of High Luminosity LHC (HL-LHC), is scheduled to begin operations in June 2030, and to run for about a decade.
“This is a very important moment. From Monday, we will be entering a new phase,” HL-LHC project chief Markus Zerlauth told reporters.
“We still have lots of physics questions without answers. There are still many discoveries to be made.”
The goal is to increase the “luminosity” (the total number of collisions produced over a given period) by a factor of 10 compared to the LHC.
The total cost of the upgrade is expected to tick in at 1.2 billion Swiss francs ($1.5 billion USD).
That will be covered by CERN membership fees, along with in-kind contributions, making up 10-15% of the total, including from the United States, Japan, Canada and China.
The upgrade will require fully replacing the components in 1.2 kilometres of the 27-kilometre tunnel.
New superconducting magnets, capable of further concentrating the particle beams, will be installed to increase the number of collisions.
Once operational, between 140 and 200 collisions will occur each time two packets of particles meet inside detectors in the tunnel, up from 60 currently.
Overall, “the increased number of collisions will allow us to collect up to 100 times more data”, Zerlauth said.
The number of collisions will be so high (several billion per second) that it will be impossible to store all the data produced.
Which collisions should be recorded will need to be selected in real time — a task that will be entrusted to artificial intelligence systems capable of identifying the most promising events.
But “AI does not replace physicists”, insisted Nedaa-Alexandra Asbah, a research physicist at CERN’s ATLAS experiment, which helped discover the Higgs Boson using the LHC.
“It is a powerful tool that helps us make better use of the data.”
The HL-LHC aims to deepen fundamental knowledge, which is CERN’s primary mission.
“We want to look for new particles,” said Filip Moortgat, the operations coordinator for CMS — and the LHC detector designed to explore a wide range of physics fields, including the search for other dimensions and the quest for dark matter particles.
Scientists believe that ordinary matter such as stars, gases, dust, planets and everything on them accounts for just 5% of the universe.
The rest is believed to consist of dark matter (27%) and dark energy (68%), which are two invisible components that scientists have yet to detect or directly observe.
The 2012 discovery of the Higgs boson provided an important piece of the puzzle: it broadened science’s understanding of how particles acquire mass and earned physicists Peter Higgs and Francois Englert the 2013 Nobel Prize for Physics.
Once the upgrade is completed, CERN hopes to dramatically expand its understanding of how the “God particle” works, with the HL-HLC expected to produce around 380 million Higgs bosons over its lifetime, compared to 55 million found since LHC operations began in 2008.
The lab’s main hope meanwhile is to produce two Higgs Bosons simultaneously, which would be a first, and see them interact, Asbah said.
This, she said, “may provide clues about how our Universe evolved shortly after the Big Bang.”
Monday, May 25, 2026
The CERN Council Decides To Update European Strategy For Particle Physics
Following more than two years of intense work of the European particle physics community under the auspices of the European Strategy Group, the CERN Council updated the European Strategy for Particle Physics, which sets out an ambitious scientific vision for the field. The 2026 Strategy update offers a clear path to maintain European leadership in high-energy physics while attracting global collaboration to CERN, advancing technology and bringing many potential benefits to society. The recommendations address a broad range of topics and goals relating to research in high-energy physics in Europe and beyond.
The aim of this Strategy update, initiated in March 2024, was for the particle physics community to develop a concrete plan for greatly advancing knowledge in fundamental physics through the construction of a new flagship project at CERN. Following extensive consultation among particle physicists in Europe and beyond, and the consideration of more than 260 written submissions, the Strategy recommendations were submitted to the CERN Council in December 2025.
Furthering our understanding of the Higgs boson has been a driving force behind the planning for the long-term future of particle physics. The discovery of the Higgs boson at CERN’s Large Hadron Collider (LHC) in 2012 marked the beginning of a new era in particle physics. It confirmed a spectacular prediction of the Standard Model of particle physics and provided a radical new tool to explore outstanding mysteries about the content, structure and evolution of the Universe.
The Strategy recommendations confirmed that the full exploitation of the scientific potential of the LHC through the completion of its high-luminosity upgrades remains the highest medium-term priority for European particle physics. For the longer term, the electron–positron Future Circular Collider (FCC-ee) was recommended as the preferred option for the next flagship project at CERN, thereby maintaining Europe’s leadership in the field.
The FCC-ee would offer the broadest exploratory programme in fundamental physics, with outstanding discovery potential. It would provide a visionary physics programme addressing many of the open questions in particle physics, notably about the Higgs boson, that are critical to understanding the foundations of the Standard Model and opening up opportunities for discovering new physics beyond the Standard Model. At the same time, the FCC-ee would drive the development of new technologies and train thousands of early-career scientists, engineers and technicians.
The 2026 update of the European Strategy builds on the previous update in 2020, which had already emphasised the importance of ensuring Europe’s continued scientific and technological leadership, and recommended an electron-positron “Higgs factory” as the highest-priority next facility after the LHC reaches the end of its operational lifetime in 2041. Based on the 2020 Strategy update, CERN and international partners conducted a feasibility study for a possible Future Circular Collider that was published in March 2025 and reviewed by the CERN Council in November 2025.
In addition to updating the Strategy, the Council has invited the CERN Management to initiate discussions with the relevant authorities and entities in the Member and Associate Member States, as well as non-Member States and the European Union, with a view to developing a financially feasible funding plan for the possible FCC-ee project. In the next two years, the CERN Management will provide annual reports on the implementation of the Strategy update and the necessary information to support national decision-making processes so that the Council will be in a position, by 2028, to take a decision on the FCC-ee, taking into account elements such as the scientific, technical and financial feasibility of the project, as well as results from the public consultation exercises in CERN’s Host States, France and Switzerland.
“The high-energy physics community and the CERN Council have been united for this critical update of the European Strategy for Particle Physics, and the FCC-ee has emerged as the preferred flagship project to maintain CERN’s world-leading role in collider physics and technology in the decades to come,” said Costas Fountas, Council President. “I wish the CERN Management the greatest success in implementing the Council resolution between now and the 2028 target decision date .”
“The European Strategy reiterates the critical importance of the High-Luminosity LHC, which will use advanced accelerator and detector technologies to fully exploit the scientific potential of this incredible machine in the coming years,” said Mark Thomson, CERN Director-General. “Beyond HiLumi LHC, the FCC-ee would be a visionary global research infrastructure for the next decades that will deepen our knowledge of the fundamental building blocks of the Universe through ultra-precise measurements of the Higgs boson and other elementary particles. CERN’s task now is to steer this unprecedented project towards a decision by the CERN Council.”
“The Strategy process has seen a very strong engagement of the particle physics community and has led to a very clear conclusion: the FCC-ee, if approved, would deliver the world’s broadest high-precision particle physics programme, its technical feasibility has been demonstrated by the comprehensive FCC Feasibility Study and its scope and cost are well defined,” said Karl Jakobs, Strategy Secretary. “It would also pave the way for a possible future hadron collider reusing the tunnel and much of the infrastructure, providing direct discovery reach well beyond the 10 TeV parton energy scale.”
